Collection fast cloners and non-cloned objects about cloning HOT 3 OPEN

hmm, but what would happen if cloneInternal() returns null? If we don't add the 
item, the cloned list will contain less items than the original

It would. But adding null is likely going to cause more issues then a different 
sized collection. If an object was set up to not be cloned and set to null- and 
since that is behavior explicitly set up I would think the cloner user would 
expect the collection to be smaller.

maybe it is worth filtering out nulls and see how it goes. Seems to me to be a 
bad practice if an instance in a list is configured to be null-ed instead of 
cloned. But if it is so, maybe it is better to filter it out.